Technical Field
The present invention relates to a unidirectional close-talking microphone and a microphone cap.
Background Art
Unidirectional close-talking microphones are used close to the mouths of talkers. An example of the close-talking microphones is one attached to a headset. Close-talking microphones are often used at outdoor events.
A unidirectional close-talking microphone collects popping noise caused by plosive sounds if the directional axis of the microphone is disposed toward the mouth of a talker. Thus, the angle of the directional axis of the unidirectional close-talking microphone is adjusted relative to the talker to avoid collection of popping noise.
In a high level of ambient noise, the directional axis of the unidirectional close-talking microphone must be directed toward the mouth of the talker to collect the clear voice of the talker certainly.
Ideally, the directional axis of the microphone should be directed away from the mouth of the talker at a low level of ambient noise, and should be directed toward the mouth at a high level of ambient noise. Such a configuration can collect the clear voice of the talker at any level of ambient noise.
It is known that bidirectional microphones can collect less noise than unidirectional microphones. Specifically, when noise is generated in all directions, the noise level collected by a bidirectional microphone is approximately ⅓ of that collected by a unidirectional microphone. That is, the anti-noise ability of bidirectional microphones is better than that of unidirectional microphones.
Thus, the noise level collected by a microphone in a high level of ambient noise can be reduced through shift of the directionality of the microphone from unidirectionality to bidirectionality.
A requirement for unidirectional close-talking microphones mounted on headsets is a simple configuration that can vary the directionality and the orientation of the directional axes.
Microphones have been known that have caps covering the sound collectors of the microphone units and being rotatably supported by the casings of the microphone units (for example, Japanese Unexamined Patent Application Publication No. 2012-169886 (hereinafter, Reference 1)).
Reference 1 does not describe a configuration that can vary the directionality and the orientation of the directional axis of the microphone.
Microphones have been known that have multiple acoustic-pressure communication holes in the front and side faces of cabinets, and can continuously vary the directionality from unidirectionality to nondirectionality through sliding of shutters, which is in contact with the interior or exterior of the cabinets (for example, Japanese Unexamined Utility Model Application Publication No. 62-86796 (hereinafter, Reference 2)).
Other microphones have been known that can vary the degree of projection of the microphone units depending on the operating mode set by mode switchers (for example, Japanese Unexamined Patent Application Publication No. 2000-184490 (hereinafter, Reference 3)).
Unfortunately, the microphones according to References 2 and 3 cannot vary the orientation of the directional axes.
Video cameras have been known that mix audio signals from multiple microphones having different directionalities at mixing ratios corresponding to the zoom ratios of imaging lenses (for example, Japanese Unexamined Patent Application Publication No. 1-321780 (hereinafter, Reference 4)).
Unfortunately, the video camera according to Reference 4 requires multiple microphones and thus inevitably has a complicated configuration.